Age hardening austenitic steel



Patented Aug. 10, 1954 UNITED STATES PATENT OFFICE 2,686,116 AGE HARDENIN G AUSTENITIC STEEL Reinhold Schempp, Clay, Peter Payson, New York, and Joe Gin-Young Chow, Long Island City, N. Y., assignors to Crucible Steel Company of America, New York, N. Y., a corporation of New Jersey No Drawing. Application June 18, 1952, Serial No. 294,260

11 Claims. (01. 75-128) .1 This invention pertains to improvements in about 0.15 to 0.45% phosphorus into steel of austenitio steels, and provides a relatively high approximately the composition given above, the

carbon, high phosphorus, steel of this type which necessary solution temperature can be lowered is age hardenable to a minimum of C 32 and appreciably from the undesirably high temperup toabout C 50 Rockwell depending upon the ature required for the steel in the absence of analysis, and which is further characterized by this phosphorus content. Depending on the high strength and corrosion resistance at both phosphorus content, the necessary solution temroom and elevated temperatures. perature can be lowered to about 2l50 F. with Objects of this invention are: to provide moderate amounts, say about 0.20%, and even to austenitic age hardenable steels which are useful 1950 F. when amounts of about 0.4% phosfor applications where high strength at room .phorus are used. temperature combined with low magnetic per- We have found that the high hardness of the I meability are required, as .for studs, gears, steelof this invention cannot be obtained merely crankshafts, and so on, in non-magnetic power by the use of phosphorus in the steel, as shown plants of submarines; for retainer rings on in Table I. rotors of electric generators; and so forth; also Table I where hardness and resistance to softening at elevated temperatures upward of 1300 F. ,combined with good resistance tooxidation and cor- LOW CARBON AUSTENITIC STEELS WITH PHOSPHORUS [Solution treated at 2150" F. and 2300 F. and water quenched; aged at rosion at such temperatures are required, par- 1200; 130m; 1400 r. for 16 hour ticularly in combustion products .of leaded gasoline, as for automotive exhaust valves, valve Bar 0 P Si N N seats, and similar parts; and finally, where high strength at temperatures upward or 1100 F. is 33331133131331: :8? iii :53 :33 it; i312 iii required together with resistance to oxidation at v these temperatures, as for steam power plant and gas turbine parts. C Rockwell Hardness Another object of this invention is to provide M an austenitic steel which is hardenable to a M13915 Bar 3913 minimum of C 32 Rockwell, or 300 Brinell. ,30 Another object of this invention is to provide 00" F. 2,150 F. 2,300F. an austenitic age hardenable steel which can be hardened to a minimum of C 32 Rockwell by fig f 'fafl igh 51 g l g 3 use of a solution temperature (no higher than Aged 1,300F.l6 hours 8 7 20 21 22000 F. Aged 1,400 F.l6 hours 9 8 19 19 In a co-pending application of one of the present inventors, Serial No. 222,736, filed April Evidently although some hardening is attain 20 95 there are disclosed austemtic steels able in low carbon steel containing about 0.27 containing; 04 to 1 5%,carbOn; v12 to 30% chro P, the attainable hardness is considered insufmium; Oto 25% nickel; 0.1 to 25% mangane ficient for the parts We wish to make from a the Combined nickel and manganese content" hardel'lable austenitic Steel. IOWEVGI, When Comprising- 3 to 0 to 5% silicon; balance higher carbon is used in the steel along with substantially iron, which are ageg-hardenable to high phOsphoms the dashed harmless of at least 32 Rockwell by a heat treatment C 32 Rockwell can be obtained as shown in consistingofsolution treating atabout ,2300 F. Table I1 and quenching, and thereupon aging at about Table II l3 0 F. An app b deterrent Q the used EFFECT OFCONATTAINABLE nARDNassINAUsTEN- such hardened St l i the V y h i n ITIC C-Mn-Ni-Cr STEEL'S CONTAINING rnosrnoaus temperatiure required w "modern [Specimens solution treated at 2150 F., water quenched, and aged at nace equipment and design it 15 not easy to heat 1250 M16 -l treat large quantities or" parts at such high tem- I 1 v I C Rockwell peratuies, pa iticulariy LI the parts are sizeable. Hardness Furthermore, the solidus temperature of such Bar 0 Mn P Ni N steel is not much above 2 350,F. Thus the solu- As After tion temperature'is dangerously close to the tem- Quenched Aging perature at which the steel begins to melt, and u bl 9.1 .21 .32 2.2 20.3 .20 21 29 r e s co (1210 e haraid tner lore 1n the i 83 4'0 220 M 23 44 handling of such steel at the temperature re- 9.0 .90 3.7 2116 45 quired for proper solution treatment for the de- 2g .o o. l sired hardening. i 5.1 .36 .53 I 3.8 21.6 .22 29 I 49 Now we have discovered that by introducing I We therefore, set 0.30% as the low limit for carbon in our steel. The high limit for carbon is established by forgeability and for forgeable steels we generally set the upper limit for carbon at 0.80%. However, for castings we may use as high as 1.5% carbon.

The eflect of phosphorus on the attainable hardness of the steel after a solution treatment at 2150 F. and aging at 1250 F. is shown in Table III and Table IV.

steels of the co-pending application it is necessary to solution treat at about 2300 F. in order to develop a hardness of C 32 Rockwell or higher in the steel after aging. When a minimum of about 0.15% phosphorus is in the steel, however, adequate hardness may be developed with solution treatments no higher than 2200 F., the higher the phosphorus, the lower the necessary solution temperature. This is illustrated by data in Table V.

Table V EFFECT OF PHOSPEORUS ON THE SOLUTION TEMPERATURE NECESSARY FOR DEVELOPING ADEQUATE HARDNESS IN O-Mn-Ni-Cr AUSTENITIC STEEL [Specimens quenched from indicated solution temperature and aged at 1,250

F. for 16 hours.]

"0 Rockwell Hardness Bar 0 Mn r Si Ni Cr M0 N 2,000" 21150" As As As Quenched Ag ed quenched A g e d Quenched A ge d 7. 8 .40 7. 3 1 22. 1 1. 8 .06 23 23 21 23 21 32 4. 8 19 19 3. 8 2O. 6 07 32 33 32 35 28 13 5. O i 21 58 3. 8 21. 4 22 37 22 43 7. 5 23 47 7. 4 22. 2 1. 8 O5 23 23 32 23 4.0 1. 9 33 4O 3. 8 21. 5 20 31 28 42 21 47 1. 1 38 33 9. 3 21. 1 26 27 27 43 22 17 7. 5 .41. 36 7. 3 21. 5 1. 7 07 27 26 38 W1 47 1.4 .44 .39 9.8 21.0 .15 26 27 41 26 48 Table III EFFECT OF PHOSPHORUS ON ATTAINABLE HARD- NESS OF MEDIUM CARBON AUSTENITIG Ah xi-lr STEELS [Specimens solution treated at 2150 F., water quenched, and aged at 1300 F. for 16 hours] G Rockwell Hardness S1 Ni Cr N As After Quenched Aging Table IV EFFECT OF PHOSPHORUS ON ATTAINABLE HARD NESS OF HIGH CARBON AUSTENITIC C-Mn-Ni-Gr STEELS [Specimens solution treated at 2150 F. water: quenched, and aged at 125o F. for 16 hours] C Rockwell Hardness As After Quenched Aging As stated earlier, in the high carbon, Mn-Ni-Cr Furthermore, whereas with the low phosphorus steels of the co-pending application it is necessaryto cool rapidly as in a water quench from the solution temperature in order that the desired hardness may be attained in the stee1 after it is aged, we have found that when phosphorus over about 0.15% is present in the steel, the desired hardness over C 32 Rockwell may be attained in the steel after aging even though the cooling rate from the solution temperature is somewhat retarded as in an oil quench, or even air cool of sections under about 1 inch thick. This obviously is of considerable advantage in the heat treatment of large sections which would suffer much less distortion when quenched in oil than when quenched in water.

Although the balance of the composition in addition to carbon and phosphorus is not restricted especially, it is desirable that the austenite forming elements manganese, nickel and nitrogen be present in sufiicient amounts to assure a stable austenitic structure in the steel.

Manganese may be present within the range of 0.5 to 15% and nickel may be present within the range of 3 to 25%, and the sum of the two within the limits of 9 to 30%. Nitrogen is generally over 03% and may be present up to about 0.40%.

Silicon is always present in the steel for deoxidation purposes and may be present up to about 3% for improving the resistance of the steel to oxidation at elevated temperatures.

Chromium is generally present in our steel from about 15 to 30% to provide corrosion and oxidation resistance. As the chromium is increased, we generally increase also the sum of manganese and nickel so that the steel will have a stable austenitic structure substantially free of ferrite.

When the steel is to be used under high stress at elevated temperatures we generally include up to about 3% of either one or both of the carbide forming elements molybdenum and tungsten.

Since the steel may be machined in the hardsulfur exhaust y balance 1c of the nt than nitrogen up to about 0.3

balance substantially iron. to be used for automotive similar parts, we generall ition with carbon in the micld ger amou igh percente analysis of Bar Table VII 0%; silicon up to about bout 0.4%; sulfur up to metal of the group molybdenum and 3%; balance substantially For steel although we may also use a h 17 to 25%; up to about 0.3%

valves and 5 the compos range and managanese in lar nickel age of nickel as shown in th 4123 in the table below.

um from about 20 to 3 3%; nitrogen up to a about 0.3% tungsten up toabout 5 iron.

PROPERTIES OF STEELS SUITABLE FOR EXHAUST VALVE SERVICE we may position up to to improve machinability. We may use different proportions of the elerbon, manganese, phosphorus, silicon, chromium, molybdenum (or tungsten),

regoing ge of analysis: ca

with high strength, have phosphorus about 0.2 to

ut 1%; chromium about 7 18663342 e r .3 id... m g n e u o m a t aa 3 O r 7 mmum m b mm 9S lw e 6 a Wm nmfim r n D o 3 1g ak m a c n h m... ucaacacc mm m p... Ln m .m r; u 8 r g r o 0 d .3 W3 u e o b e a ,EF 1 m m7 3 A m amm w mnnmmmnm W mm m m 0 a maaaaaaa m amm m S e. O O mm w 3 0 33 3 .32 .3333 .332 .3 1 f n e 7 o tb h b h e a ,0 Imm I I Immmm I Immw I Im g 3 5 6Y0 08909035 6 a n t W A N m mudIu ImLL I .I I 1LLL .I M1LL m T. u I 337.3%...3 mawm W m 3. 3 I :I I II 32 wm m o 3 II III II II mmamnuzd. oPtOh 5 N t .sbs n m I Inn I I I mn I Imu I I b 0 .311 r 89888 o w a db n" "n" I I Fmo R c 11111 .3, N II III I II 7 2 4 mm W m w a II III II II 4I5 &a8 &&a w t h s m a0 a 0 5 32 0111 6 r n 5550500005555500505 a Oh3 nb L A 1 a .7.6.3.Q5.L5.09.0.0.& h tl a a MN 9999BBBB ml mmm %%%%223214332332 is 0 TO .e P I 0 3 S T m 9624074170259540671 3 m1 mm m a w m anaaaaaa m mm m wumuuummaaunamwmmmn 3 u e c I 1 1% B S S H SL S t a .1 e a p E P aW t I I 0000000000000000000 a m a w Tu mm m wmwmmmmmmmmmmmmmmmm m mm a D n 1 m3 first? mmmmmmmmmmmmmmmmmmm e r V 3 3 '1 e a P d .5 n ad 8 0G e ,5 e 0 M RN m g k e b 0 C 0 PE d 000000 0000000 m e m m u a R 5554444 Mm m w 3 3 s T W 3333.11.11. 3 .3 3.3;. was h 4mm w m YD. 11 11111 1 y f p ath 3 IG t m h t e m m w m 1 a 3 an an aaaaaaa m a. m n a e E H t h u atl Mo 0 mm m ahib Rm 3 3 m w E m n III .1 e 10 e I I I mhm PN at m 2. amIaIm mm n n D m a an Mara agmfwmi N T tat Md m o mus m A m n FF FFFFFF 1 m a w a a n a at g T S U 01 011990 .m e s H m e m m w 2 2 2 11 2 2 2 2 1 1 2 a m w N m I e or a A I IIIIIIIIIIIIIII n e H 3 r w e 0 e1 m n c a m aaaiiurrmaauunrn r 1 0 E .m M144. 44444444455555 mus mum mm M w amaamaaaaaaaaaaaaaa ened condition after final heat treatment include sulfur in the steel com about 0.30%

ments ca nickel and nitrogen in the steel depending on the a plication. For an application requiring a no rred ran ganese about 1 to 5%; nickel about 8 The low permeability steels of the fa h characteristics together the following prefe bon about 0.3 to 0.5% 0.4%; man to 15%; silicon up to abo For applications where strength at high temhardness is about 1250/1300 F. good hardness peratures for long time service is required, we is developed with aging temperatures as high as generally include molybdenum (or tungsten) 1500 F. Furthermore, steel which has been in the composition as stated above. Some data aged at 1300 F. can be reheated for ashort on steels suitable for high temperature applica- 5 time at temperatures as high as 1700 F. withtions such as steam power plant and gas turbine out suffering much less of hardness. Some data parts are given in Table VIII. on the resistance of the steels of this inven- Table VIII PROPERTIES OF STEEL SUITABLE FOR SERVICE AT l,200 F. UNDER STRESS Bar 0 Mn P Si Ni Cr Mo ROOM TEMPERATURE PROPERTIES n 0.2% Elong. Heat O Tensile Red. V-Yotch Bar Treat- Rock. g fig Strength, Area, Izod, ment Hard. p. s p. s. 1. pernt percent it.-lbs.

3933 BB 35 98,000 156,000 18 6 25.0 7 BO 32 81, 000 141,000 27 1 30.5 BB 36 96, 000 154, 000 21 4 23. 5 7 BO 33 77,000 137, 000 26 6 32. 5 13 BO 33 000 140, 000 22 6 27. 5

STRESS RUPTURE PROPERTIES AT 1,200 F.

1 Heat Treatments: BB2,150 F., Water quench; aged 1,500 F.-16 hours. B0- 2,150 F., water quench; aged 1,300 F.l6 hours; plus 1,700 F.-2 hours.

2 Norm-Test piece with 60 degree V-notch, diameter base of notch .252 in. with gage section .357 in. diameter; .005 in. radiusbasc of notch.

A preferred range of analysis for steels of this tion to softening at high temperatures are type is: carbon about 0.45 to 0.7%; phosphorus shown in Table IX.

Table IX EFFECT 'OF HIGH TEMPERATURE HEATING ON HARDNESS OF C-Mn-P-Ni-Cr STEELS {Specimens solution treated at 2,150 -F., water quenched, and aged as indicated.]

"0 Rockwell Hardness A 1 Bar 0 Mn 1? Si l\1 Cr Mo Aged Aged Aged 1,300;%F., As Q 1,300F., 1,10oF., 1,500F., fi

16hours 16 hours 16 hours 03;

' 2hrs. I,

.51 75 .23 .47 7.4 22.2 1.8 23 40 as 33 32 .61 7.5 .22 .42 7.3 22.0 1.9 21 11 35 34 as .72 7c .26 .45 7.3 22.8 1.2 27 41 37 31 33 .53 7a .41 .36 7.3 21.5 1.7 24 4e 12 40 39 .58 7 5 .43 .as 7.5 21.2 1.6 25 46 43 3s 39 about 0.2 to 0.45%; manganese about 5 to 12%; What we claim is: nickel about 4 to 18%; chromium about 20 to 1. Age hardenable austentic steel character- 30%; silicon up to about 3%; metal of the group ized in being hardenable to a minimum of about molybdenum and tungsten, about 1 to 3%; nitro- 7'.) C 32 Rockwell after solution treatment at a gen up to about 0.4%; sulfur up to about 0.3%; temperature no higher than 2200 F. and subbalance substantially iron. sequent aging at about 1300 F. for about 15 It is of interest that the steels of this invenhours, said steel containing about: 0.3 to 1.5%

tion are quite resistant to averaging. Although carbon; 0.15 to 1% phosphorus; 0.5 to 15% manthe optimum aging temperature for maximum ganese; 3 to 25% nickel, the sum of nickel and manganese being about 9 to 30%; 15 to 30% chromium; up to about 3% silicon; up to about 3% of metal selected from the group consisting of molybdenum and tungsten; up to about 0.4% nitrogen; up to about 0.3% sulfur; and the balance iron.

2. A precipitation hardened, austenitic alloy v steel, having a hardness of at least C 32 Rockwell, said steel having substantially the following composition: 0.3 to 1.5% carbon; 0.15 to 1% phosphorus; 0.5 to 15% manganese; 3 to 25% nickel, the sum of nickel and manganese being about 9 to 30%; 15 to 30% chromium; up to about 3% silicon; up to about 3% of metal selected from the group consisting of molybdenum and tungsten; up to about 0.4% nitrogen; up to about 0.3% sulfur; and. the balance iron.

3. A cast article made of precipitation hardened, austenitic alloy steel, having a hardness of at least C 32 Rockwell, said steel having substantially the following composition: 0.3 to 1.5% carbon; 0.15 to 1% phosphorus; 0.5 to 15% manganese; 3 to 25% nickel, the sum of nickel and manganese being about 9 to 30%; 15 to 30% chromium; up to about 3 silicon; up to about 3% of metal selected from the group consisting of molybdenum and tungsten; up to about 0.4% nitrogen; up to about 0.3% sulfur; and the balance iron.

4. A forgeable, age hardenable, austenitic steel, characterized in being hardenable to a minimum of C 32 Rockwell after solution treating at a temperature no higher than 2200 F. and subsequent aging at about 1300" F. for about 15 hours, said steel having substantially the following composition: 03 to 0.7% carbon; 0.15 to 0.45% phosphorus; 0.5 to 15% manganese; 3 to 25% nickel, the sum of nickel and manganese being about 9 to 30%; 15 to 30% chromium; up to about 3% silicon; up to about 3% of metal selected from the group consisting of molybdenum and tungsten; up to about 0.4% nitrogen; up to about 0.3% sulfur; and the balance iron.

5. A forgeable, age hardenable, high strength, low permeability steel, which is age hardenable to a minimum of about C 32 Rockwell after solution treating at a temperature no higher than 2200 F. and subsequent aging at about 1300 F. for about 15 hours, said steel having substantially the following composition: 0.3 to 0.5% carbon; 0.2 to 0.4% phosphorus; 1 to 5% manganese; 8 to 15% nickel; 17 to 25% chromium; up to 1% silicon; up to 0.3% nitrogen; up to 0.3% sulfur; balance iron.

6. A precipitation hardened, austenitic alloy steel, having a hardness of at least C 32 Rockwell, said steel having substantially the follo. ing composition: 0.3 to 0.7% carbon; 0.15 to 0.45% phosphorus; 0.5 to 15% manganese; 3 to 25% nickel, th sum of nickel and manganese being about 9 to 30%; 15 to 30% chromium; up to about 3% silicon; up to about 3% of metal selected from the group consisting of molybdenum and tungsten; up to about 0.4% nitrogen; up to about 0.3% sulfur; and the balance iron.

7. A precipitation hardened, austenitic alloy steel, having a hardness of at least C 32 Rockwell, said steel having substantially the following composition: 0.3 to 0.5% carbon; 0.2 to 0.4% phosphorus; 1 to 5% manganese; 8 to nickel; 17 to 25% chromium; up to 1% silicon; up to 0.3% nitrogen; up to 0.3% sulfur; balance iron.

8. A forgeable, age hardenable steel adapted for automotive exhaust valves and similar parts, said steel being hardenable to a minimum of about 0 38 Rockwell on solution treating at a temperatur no higher than 2200 F. and subsequent aging at about 1300 F., and having good corrosion and oxidation resistance at elevated temperatures, said steel having substantially the following composition: 0.4 to 0.7% carbon; 0.15 to 0.45% phosphorus; 1 to 12% manganese; 3 to 25% nickel, the sum of manganese and nickel being about 9 to 30%; 20 to 30% chromium; up to 3% silicon; up to 0.4% nitrogen; up to 0.3% sulfur; up to 3% of metal selected from the group consisting of molybdenum and tungsten, balance iron.

9. An article made of a precipitation hardened alloy steel, having a hardness of at least C 38 Rockwell, said steel having substantially the following composition: 0.4 to 0.7% carbon; 0.15 to 0.45% phosphorus; 1 to 12% manganese; 3 to nickel, the sum of manganese and nickel being about 9 to 20 to 30% chromium; up to 3% silicon; up to 0.4% nitrogen; up to 0.3% sulfur; up to 3% of metal selected from the group consisting of molybdenum and tungsten, balance iron.

10. A forgeable, age hardenable steel, suitable for service under high stress at elevated temperatures upward of 1100 F., said steel being hardenable to a minimum of C 32 Rockwell on solution treating at a temperature no higher than 2200 FL, and subsequent aging at about 1300 F., said steel having substantially the fol lowing composition: 0.45 to 07% carbon; 0.2 to 0.45% phosphorus; 5 to 12% manganese; 4 to 18% nickel; 20 to 30% chromium; up to 3% silicon; 1 to 3% of metal selected from the group consisting of molybdenum and tungsten; up to 0.4% nitrogen; up to 0.3% sulfur; balance iron.

11. An article made of a precipitation hardened alloy steel, having a hardness of at least C 32 Rockwell, said steel having substantially the following composition: 0.45 to 0.7% carbon; 0.2 to 0.45% phosphorus; 5 to 12% manganese; 4 to 18% nickel; 20 to 30% chromium; up to 3% silicon; 1 to 3% of metal selected from the group consisting of molybdenum and tungsten; up to 0.4% nitrogen; up to 0.3% sulfur; balance iron.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,495,731 Jennings Jan. 31, 1950 2,528,637 Clarke Nov. '7, 1950 

1. AGE HARDENABLE AUSTENTIC STEEL CHARACTERIZED IN BEING HARDENABLE TO A MINIMUM OF ABOUT "C" 32 ROCKWELL AFTER SOLUTION TREATMENT AT A TEMPERATURE NO HIGHER THAN 2200* F. AND SUBSEQUENT AGING AT ABOUT 1300* F. FOR ABOUT 15 HOURS, SAID STEEL CONTAINING ABOUT: 0.3 TO 1.5% CARBON; 0.15 TO 1% PHOSPHORUS; 0.5 TO 15% MANGANESE; 3 TO 25% NICKEL, THE SUM OF NICKEL AND MANGANESE BEING ABOUT 9 TO 30%; 15 TO 30% CHROMIUM; UP TO ABOUT 3% SILICON; UP TO ABOUT 3% OF METAL SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM AND TUNGSTEN; UP TO ABOUT 0.4% NITROGEN; UP TO ABOUT 0.3% SULFUR; AND THE BALANCE IRON. 